/// vec初始化
pub fn test() {
    let a: Vec<i32> = Vec::new();
    let b: Vec<i32> = vec![];
    println!("{:?}, {:?}", a, b);

    let a2: Vec<i32> = vec![1i32, 2, 3];
    let a3: Vec<i32> = vec![0; 10];
    println!("{:?}, {:?}", a2, a3);
}
